Wastewater from animal tissue processing operations presents several challenges to operators. Wastewater from the animal rendering facility is collected from several different sources, including floor washing, equipment cleaning and sanitation, carcass rinsing, and several other related flows derived from the processing of live animals. The resultant wastewater mixture includes solids in the form of animal tissues, as well as animal tissue components, including fats, oils, greases, and proteins which are too small to be easily screened. Nevertheless, such components contribute to total chemical oxygen demand (COD) and biological oxygen demand (BOD), which represent threshold limitations for the facility's wastewater output to municipal or other water treatment systems. Reduction of such constituents from the wastewater stream can therefore address wastewater effluent quality thresholds and may even serve to reduce municipal wastewater permitting fees where COD and BOD of the wastewater effluent may be reduced.
Additionally, certain of the animal matter components in the wastewater stream may have value in the form of additives for livestock feed and other possible uses. Recovery of such components from the wastewater stream may accordingly present a revenue stream for the facility operator, while simultaneously reducing wastewater effluent volumes. Such materials may be considered “byproducts” of the animal rendering process, with their own commercial value.
Oftentimes, the animal rendering byproducts mix with the wastewater stream into emulsions, which pose a problem for facilities attempting to recycle water and stay in compliance with permissible discharge limits. Separation of fats, oils, greases, and proteins from emulsions by mechanical separation means, such as decanters, centrifuges, and the like has proven to be largely ineffective. Consequently, there exists a need to chemically promote the “breaking” of emulsions formed in animal rendering process wastewater streams, so that the valuable fat, oil, grease, and protein byproducts may be effectively and efficiently recovered.